Hollow airfoils are well known in the art. They may be cast as a single structure with internal cooling cavities, or they may be made from a plurality of pieces which are bonded together. For example, it is known to make the airfoil in two pieces: a suction side half and a pressure side half. These halves, when bonded together, may form, for example, one or more longitudinally extending cavities therebetween through which cooling air is passed. A trailing edge portion of the airfoil may include a plurality of pedestals extending across a gap between the pressure and suction side wall to form cooling passageways therethrough. Cooling air from a hereinabove mentioned longitudinal cavity is often directed rearwardly through the trailing edge passageways between the pedestals and exits through slots in the trailing edge of the airfoil.
Tube-like inserts may be disposed within the hereinabove mentioned longitudinal cavities and often have small holes therethrough to direct cooling air from within the tubes against various portions of the airfoil pressure and suction side walls. Also, inserts may be bonded to the inside surfaces of the cavities and be spaced therefrom, such as by ribs or pedestals, to define cooling air passages therebetween. If these inserts come unboned and pull away from the wall they can disrupt the proper flow of cooling air, such as by blocking or closing off other passages within the airfoil. This could cause overheating and failure of the airfoil. Several patents typical of the prior art as discussed above are U.S. Pat. Nos. 3,700,418; 3,554,663; 3,994,622; 4,019,831; 4,022,542; and 4,183,716.